Remove ConsensusData from Block

[fyrchik]

Close #1738 .

[codecov]

Codecov Report

Merging #1792 (ba55f4c) into master (e66d369) will decrease coverage by 0.09%.
The diff coverage is 86.06%.

@@            Coverage Diff             @@
##           master    #1792      +/-   ##
==========================================
- Coverage   83.61%   83.52%   -0.10%     
==========================================
  Files         284      283       -1     
  Lines       22099    22166      +67     
==========================================
+ Hits        18479    18514      +35     
- Misses       2492     2523      +31     
- Partials     1128     1129       +1     

Impacted Files	Coverage Δ
pkg/interop/convert/convert.go	0.00% <0.00%> (ø)
pkg/consensus/block.go	85.71% <66.66%> (-4.77%)	⬇️
pkg/core/block/header.go	82.50% <82.50%> (+11.07%)	⬆️
pkg/core/block/block.go	81.17% <94.11%> (-2.01%)	⬇️
pkg/consensus/consensus.go	68.35% <100.00%> (-0.20%)	⬇️
pkg/core/blockchain.go	79.77% <100.00%> (+0.02%)	⬆️
pkg/core/dao/dao.go	73.70% <100.00%> (+0.10%)	⬆️
pkg/core/interop/runtime/engine.go	100.00% <100.00%> (ø)
pkg/core/native/native_gas.go	73.91% <100.00%> (ø)
pkg/core/util.go	70.00% <100.00%> (-2.73%)	⬇️
... and 9 more

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[roman-khimov]

The first two commits don't belong here.

[fyrchik]

First commits are needed to correctly regenerate testchain, this wasn't catched when bug was introduced.

[roman-khimov]

1. It'd be nice to rename block_base.go into header.go
2. (*Blockchain).GetBlock should fail for incomplete block, we can do that with merkle root check, for empty block it'd be 0 (and thus block == header), for non-empty block it won't be 0 and we should then check for number of transactions (that should also not be zero, otherwise we only have header and can't answer GetBlock request).